Oscillating turrets or monitors have been developed and sold in the past to automatically distribute foam, water or foam-water over a specific area as determined by an angle of monitor elevation, arc of oscillation, speed of oscillation, and the foam pattern. Both automatic and manual operation has been provided. Such devices are exemplified by the Model OFC of Feecon Corp., Westboro, Mass., incorporating a clutch mechanism and two four-way valves; the Rockwood Monitor of Rockwood Systems, So. Portland, Me., incorporated a rack and pinion and gear drive; the LO-EX monitor of Walter Kidde Inc., Wake Forest, N.C., including a turbine and gear box drive; and the WOT monitor of Santa Rosa Mnfg. Co., San Jose, Calif., including a four-way valve and chain drive.
A feedback actuated four-way valve controlling a cylinder to actuate a second four-way valve is expensive. Four-way valves are invariably used) are the most trouble-prone part of the system, subject to sticking due to corrosion buildup of deposits of waterborne minerals, or waterborne particulate matter. Cylinder-driven rack and pinion gear arrangements are expensive, subject to alignment problems and require periodic lubrication. Cylinder-driven chain and sprocket arrangements are subject to chain stretch and deflection of the cylinder rod due to eccentric loading of the cylinder by the chain. Turbine and gear box drives are susceptible to sticking of the low torque turbine wheel shaft due to various mechanical problems, including corrosion and waterborne mineral deposition.
Most prior art in fluid-driven devices (going back to early steam engines) used feedback from the output of the engine to actuate a four-way valve which reversed flow to a cylinder, which in turn actuated a second four-way valve which reversed flow to the main power cylinder. Such an arrangement is effective but is very expensive.